drbd: fix max_bio_size to be unsigned

We capped our max_bio_size respectively max_hw_sectors with
min_t(int, lower level limit, our limit);
unfortunately, some drivers, e.g. the kvm virtio block driver, initialize their
limits to "-1U", and that is of course a smaller "int" value than our limit.

Impact: we started to request 16 MB resync requests,
which lead to protocol error and a reconnect loop.

Fix all relevant constants and parameters to be unsigned int.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 2704af2..b2ca143 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -1136,8 +1136,8 @@
 	int rs_in_flight; /* resync sectors in flight (to proxy, in proxy and from proxy) */
 	int rs_planed;    /* resync sectors already planned */
 	atomic_t ap_in_flight; /* App sectors in flight (waiting for ack) */
-	int peer_max_bio_size;
-	int local_max_bio_size;
+	unsigned int peer_max_bio_size;
+	unsigned int local_max_bio_size;
 };
 
 static inline struct drbd_conf *minor_to_mdev(unsigned int minor)
@@ -1441,9 +1441,9 @@
  * hash table. */
 #define HT_SHIFT 8
 #define DRBD_MAX_BIO_SIZE (1U<<(9+HT_SHIFT))
-#define DRBD_MAX_BIO_SIZE_SAFE (1 << 12)       /* Works always = 4k */
+#define DRBD_MAX_BIO_SIZE_SAFE (1U << 12)       /* Works always = 4k */
 
-#define DRBD_MAX_SIZE_H80_PACKET (1 << 15) /* The old header only allows packets up to 32Kib data */
+#define DRBD_MAX_SIZE_H80_PACKET (1U << 15) /* The old header only allows packets up to 32Kib data */
 
 /* Number of elements in the app_reads_hash */
 #define APP_R_HSIZE 15